Synthesis and Nitration of Some Thieno-fused Analogues of the Benzo[a]quinolizinium Cation

Article abstract of DOI:10.1002/jhet.5570330111

Three thieno-fused analogues of benzo[a]quinolizinium (1), thieno[3,2-a]- and thieno[2,3-a]quinolizinimn 4 and 5 and thiazolo[2,3-a]isoquinolinium (6), were synthesized by photocyclization of 1-(2-thienylvinyl)pyridinium salts 9a and 9b and 3-styrylthiazolium salt 9c, respectively. The nitration of the compounds 4, 5, and 6 occurred predominantly at positions 2, 3, and 7, respectively, while the nitro group was introduced into the 8- and 10-positions of 1 in the ratio of 68:32. The nmr and uv spectral properties and reduction potentials of 4-6 were also compared with those of the parent compound 1.